The invention relates to metamaterials that are constructed by incorporating point defects into a photonic crystal, a periodic dielectric structure that prohibits the propagation of light within a certain frequency range, or band gap. The point defects are localized structural or material changes that break the periodicity of the crystal, and which support localized electromagnetic field states that may resemble oscillating electric or magnetic dipoles.
Prior work on metamaterials has included structures formed of arrays of metallic elements. For certain wavelengths greater than the length scale of the elements, light that contacts the structure behaves as though the structure were a medium with effective electromagnetic properties. These properties may be quite different than those of naturally occurring materials or structures. For example, a microstructure that is formed from low density metallic non-magnetic conducting sheets is disclosed in Magnetism from Conductors and Enhanced Nonlinear Phenomena, by J. B. Pendry, A. J. Holden, D. J. Robbins and W. J. Stewart, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 47, No. 11 (November 1999). This structure is disclosed to provide an effective magnetic permeability μeff that may be tuned to values not accessible in naturally occurring materials for incident radiation at microwave frequencies. A mechanism for lowering the plasma frequency in metallic mesostructures into the far infrared and even up to 8.2 GHz band, thus changing the frequency range in which the effective permittivity εeff is negative, is proposed in Extremely Low Frequency Plasmas in Metallic Mesostructures, by J. B. Pendry, A. J. Holden, and W. J. Stewart, PHYSICAL REVIEW LETTERS, vol. 76, No. 25 (June 1996).
These two structures may be useful for a variety of purposes; in combination, they may provide devices with negative indices of refraction. See for example, Composite Medium with Simultaneously Negative Permeability and Permittivity, by D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, PHYSICAL REVIEW LETTERS, vol. 84, No. 18 (May 2000); The Electrodynamics of Substances with Simultaneously Negative Values of ε and μ, by V. G. Veselago, SOVIET PHYSICS USPEKHI, vol. 10, No. 4 (January–February 1968); Experimental Verification of a Negative Index of Refraction, R. A Shelby, D. R Smith, and S. Schultz, SCIENCE, vol. 292, pp. 77–79 (April 2001); and Negative Refraction Makes a Perfect Lens, by J. B. Pendry, PHYSICAL REVIEW LETTERS, vol. 85, No. 18 (October 2000).
It is desirable to develop a structure that provides some or all of the above metamaterial properties using excitation fields having frequencies in the visible light range and above. Because the material absorbtion losses are relatively high in metals for these frequencies, an alternative approach employing dielectric materials is attractive.